Thursday, May 20, 2010

Hops Pest: Eastern Comma Butterfly

A few weeks ago a number of our local hops producers were noticing large holes in some of their hops leaves. Upon closer inspection, they found spiky, white caterpillars feeding on the leaves.

Larva of Eastern comma butterfly found on hops in WNC (picture courtesy of R. Pelczar).

The entomologists at NCSU agreed that the caterpillars are larvae of the Eastern comma butterfly, Polygonia comma.

Larva of Eastern comma butterfly found on hops in WNC (picture courtesy of R. Pelczar).

Hosts plants of the Eastern comma butterfly are American elms, hackberry, nettles, false nettles and other members of the Urticacea. But, perhaps the favorite food of the Eastern comma butterfly is hops.

Beginning in the early 1900's, the Eastern comma butterfly was referred to as the "hop merchant" because hops farmers would predict the future price of hops based on the variation in the silver and gold spots on the pupae.

The larvae ranges in color from white to green-brown to black and are typically just over 1 inch long. The spikes also range in color from black to white with black tips. The larvae rest on the underside of leaves and make nests by silking together the sides of the leaf. The larvae rest during the day and feed at night.

Eastern comma butterfly larva. (Picture courtesy of Echoview Farm).

The eggs are green with vertical ridges and are laid singly or in stacks. I was lucky to find these (sorry they are not the greatest pics)!

Eggs of Eastern comma butterfly on underside of hops leaf.

Close-up of the eggs of Eastern comma butterfly. Notice the vertical ridges.

Pupae are variable in color but always have prominent ventral gold or silver spots.

The adult is an orange and brown butterfly with a wingspan of 1.75 to 2 inches. With its wings folded it looks like a dead leaf.

Life Cycle:
There are two generations per year for Eastern comma butterflies. During the summer, the new butterflies are inactive during the hot period and then become active again in the fall. The fall brood of adult butterflies overwinter and start the cycle again in the spring.

The feeding damage caused by the Eastern comma butterfly larvae ranged in the individual hops yards here in WNC. One grower experienced quite a bit of initial damage, but was able to prevent further destruction by hand-picking the caterpillars.

Growers at another farm reported shaking the bines to knock off the caterpillars and then destroying them. This appeared to work well and little damage has since been noted. This grower also applied BT (Bacillus thuringiensis, a bacterial biological control material that is labeled for Lepidopteran pests) and reported that it was effective.

Hopefully, the Eastern comma butterfly will not be a problem for our hops growers in the future. At least now we know what the pest is and how to control it.

Thanks to all the folks who helped in the identification of the larvae and for the great growers for sharing their experience and their wonderful pictures!

To learn more, read the University of Florida's fact sheet on the Eastern Comma Butterfly.


yanceyfoxfarms said...

The info regarding Comma Butterfly was very helpful...I did see a similar looking butterfly near the hops. The caterpillars we have are black with light spots, no spikes, and a lot of webbing. We are hand-picking the little rascals! So, it would be a good idea NOT to have a Butterfly Habitat near the hops?

fattymattybrewing said...

We have observed the Easter Comma butterfly caterpillar at our hopyard in Dodgeville, Wisconsin - <a href="'>Simple Earth Hops</a>. Hand picking has been our best defense.